A stretch of Main Street in front of the Calvert County Circuit Courthouse was blockaded Friday morning after someone called in a bomb threat to the circuit court switchboard at 9:27 a.m., Lt. Bobby Jones of the Calvert County Sheriff's Office said.

Jones said the building was completely evacuated by 9:45 a.m. Evacuees scattered along the street and brick walkway between the circuit and Calvert County District Courthouses awaited to re-enter the building while police investigated and walked the grounds with police dogs. Nothing was discovered, Jones said.

"It doesn't happen frequently, though probably more frequently than we'd like," Jones said. "We've had two others this year. It's actually unusual to have this many around this year's time. We go sometimes a whole year without getting a bomb threat at the courthouse."

Calvert County Sheriff Mike Evans said somebody with a male voice called and said "There's a bomb in the building," but did not give a reason for the threat.

"Friday is child-support day. It's an awful coincidence," Evans said, adding that it was unknown whether the caller had a scheduled court date. "It seems like there's a pattern here."

Bomb threats are taken seriously, Evans said, using the six-year prison sentence received by a woman who called in three bomb threats to a Wal-Mart in St. Mary's County last February as an example.

"And that's what they would get," Evans said in reference to the person who called in Friday's threat.

An ongoing investigation is being conducted by detectives from the Calvert Investigation Team, Jones said.

"It's pretty much your standard bomb threat, but we don't really have a whole lot to go on at this point," Jones said.

Evans also asked that anyone with any information related to the threat notify police.

The district court remained in session following the initial threat.

The scene was cleared by 11:15 a.m., Jones said. About 10 minutes later, units responded to the district court for an unrelated medical call, according to deputies leaving the district court.